Motor-control system.



C. P. TAYLOR.

MOTOR CONTROL SYSTEM.

APPLICATION FILED NOV-2|. m3.

1,240,623. Patented Sept. l8;1;9l7.

M Reverse.

28 27 95 3 4 Forward JZVY E'NTUR CARL 2 TJYQDH, M

rmrtriazn STATES PATENT OFFICE.

CARL P. TAYLOR, OF ROANOKE, VIRGINIA, ASSIGNOR '10 GENERAL ELECTRIC v COMPANY, A CORPORATION OF NEW YORK.

MOTOR-CONTROL SYSTEM.

Specification of Letters Patent. Patented Sept. 18, 1917.

Application filed November 21, 1913. Serial No. 802,223.

To all whom it may concern:

Be it known that I, CARL P.- TAYLOR, a citizen of the United States, residing at Roanoke, county of Roanoke, State of Virginia, have invented certain new and useful motor so as to bring it to rest quickly. This is commonly done by cutting off the supply of current and simultaneously closing aacircuit across the motor armature through a resistance so that I the motor acting as a generator willbe retarded or dynamically,

raked by the generation of current. Heretofore this hasbeen done by connecting the dynamic braking circuit through the commutator of the motor, the result often being that sparking is caused, especially when the dynamic brakin current is high and the motor field relatively weak. One of the objects of my invention is to provide means whereby the motor will be dynamically braked without carrying the braking current through the commutator.- This I accomplish by connecting a dynamic braking circuit to fixed points in the armature winding, preferably through collector rings, so that when this circuit is closed an alternating current will be generated by the motor a'cti'ng as a generator andthus bring the armature to rest in a very effective manner, the arrangement being such that the dynamic, braking circuit will be maintained closed and the circuit from the source of supply will be maintained open until the motor has been brought substantially to rest. A further object of my invention is to provide an arrangement whereby the motor will be periodically reversed and will be causedto operate at aflifierent. speed for eachdrrection of rotation by means of two field windings which have a cumulative effect for'the one direction of rotation and a difierential effect for the opposite direction, one of the windings being connected across a source of and the other connected across the motor armature. Other ob ects and purposes of my invention will appear in the which I have disclosed my invention embodied in concrete form for purposes of illustration. L

Referring to the accompanying drawings in which I have illustrated my invention diagrammatically, A represents the armature of a direct current motor having a commutator 10 and brushes 11. This motor has two field windings 12 and 13 the former being connected across the armature brushes while the latter is connect-ed across the supply circuit. The purpose of this arrangement will hereinafter appear. At the opposite end of the. armature from the commu- Dcourse of the following specification in tator I have provided two collector rings 14 I although it is obvious that my invention is machine tools, such as planers and the like,

not limited in its application to a reversible motor, nor is it limited to the generation of single phase current above mentioned, as

distinguished from three phase or polyphase currents. The switch contacts 16 for closing the alternating current circuit are closed by an electro-magnetically operated switch 17 having an operating winding 18 connected across the supply circuit and a winding 19 for holding the dynamic braking circuit closed, this latter winding being connected in shunt with the motor armature. The switch 17 is double acting, as shown, being provided with two contact members 20 and. 21, the former for bridging the. contacts 16 while the latter bridges the contacts 22 to close the armature circuit. When 'the winding 18 is energized, the contact member 21 is moved upward so as to bridge the contacts 22 and when the winding 18 is deemergized, the switch member 17 drops by gravity so that the member 20 bridges the position by the winding 19, which is connected across the armature, until the rotation-of the armature practically ceases. The

operation of the switch member 17 is thus responsive to the speed and the potential of the motor armature. A starting resistance R is provided for gradually bringing the rangement being such that the contactor is held open when the current is high and will not close until the current falls to a predetermined value. A master switch M is provided for controlling the direction of rotation of the motor and may be operated in any desired manner, either automatically, as

in the case of a planer, or manually.

In the operation of certain reversing machines, especially in the case of such machine tools as planers and the like, it is customary to operate the machines at a greater speed during the return stroke, when nowork is being done, than upon the forward or (in the case of a planer) the cutting stroke. This has commonly been done in the case of motor driven planers. by varying the field resistance at the end of each stroke. In order to accomplish this result without changing the field resistance, I have provided the two permanently connected field windings 12 and 13. The winding "13 being connected directly across the line will produce a constant magnetizing effect, while the winding 12 being connected across the mo tor armature will have its effect reversed each time the motor armature is reversed. The winding 12, therefore. will upon one direction of rotation gradually build up to as sist thewinding 13 and strengthen the field, whereas, in the 'oppositedirection of rotation, the winding 12 will gradually build up -1n opposition to the winding 13. When,

therefore, the motor gets up to full speed in one direction there willbe a field of maxi mum strength for the working stroke and when the armature'is rotating in the opposite direction for the return stroke the field will be weakened. This of course will give a low speed and full field strength during the cutting stroke and high speed and a weakened field on the reverse stroke'.without anychange whatsoever in field connec-' tions.

The arrangement of circuits and mode of operation of my device areas. follows:

With the master switch in the central posi tion the parts are in the position shown in the drawing. If now the master switch is thrown to the position marked forwardZ the-windin 18 will be energized from the positive si e of the line through the contacts 25 and 26 on the master controller to the negative side of the line. The energization of the magnet 18 causes the switch ing 13 being energized across the line, the.

motor will start and the starting resistance R graduall be cutout in a well understood manner. s the armature speeds up the field winding 12 will build up either to assist or oppose the winding 13, depending upon the direction of rotation of the armature. If the motor is operating in the for ward direction, as when it is drivin a planer on the cutting stroke, the two eld windings 13 and 14 will assist each other and the motor will operate at its lowest speed. When the master switch M is thrown over to the opposite position the winding 18 will be deenergized for an instant and the switch member 17 will drop 1 and bridge the contacts 16. The dropping of the contact 21 will open the supply circuit, while the bridging of the contacts 16 closes the dynamic braking circuit from the collector rings 14, through impedance 15, and contacts 16. The impedance 15 may be so proportioned that the dynamic braking current will be as high as the armature windings can carry, and for this reason the motor can thus be brought to rest ve guickly. .This,it will be seen, is quite d' erent from what would be the case if the braking circuit were connected. across the commutator, since in this latter case the amount of the brakin limited to anamount w ich will give substantially sparkless commutation. I have shown the impedance 15 in the form of a reactance, although either a resistance or current will be reactance may be employed to accomplish the same result. When the master switch is thrown to the opposite direction, that is, so that the contacts are in reversing position, the windin 18 will be a in energized and will ten to lift the switch member 17 and close the contacts 22. Switch' member17, however, will not be lifted to close the line circuit for the opposite directionuntil the armature has been brou ht substantiall to' rest, since the member 1 is held down y the winding 19 which is conof the motor;

stopped rotatin the winding .19 will be deenergized and t e winding 18 will move the switch member upward to close the contacts '22 and open the contacts 16. This will close the armature circuit in the opposite dlrection of rotation, the circuit now belng as'follows: From the positive side of the difference in strength between the two field windings, The motor is therefore brought to a much higher speed than before. When the master controller operates the dynamic braking circuit again closes the contacts'16 so as to bring the armature to rest quickly and the circuit for the opposite direction of rotation cannot be closed until the armature has stopped rotating.

Whlle I havedescribed my invention as embodied in concrete form and as operating 1 in a specific manner in accordance with the provision of the patent statutes, it should be understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves! to those skilleddn the art without departing from the sp1r1t 0% my invention, the scope of which is setforth in the annexed claims.

What I claim as new and desire to secure bv Letters Patent of the United States, is 1. In a control system-for electric motors, a reversible direct current motor, means for causmg the motor to operate at different speeds in the two directions, comprising two permanently connected shunt fields energized to have a-cumulativeefiect for one di- '-rectionof rotation and a difierentialefiect field wind across the line and the other across the motor armature, andmeans forreversing the;

for the opposite rotation, and means for reversmg the motor. :"2. In a control system for electric motors, a reversible direct current motor, means for causing thej "motor to operate at different speeds in sage two directions comprising two rigs one of which is connected the armature of said motor. f 3. In a control system for electric motors, a reversible direct current motor, means for causing the motor to operateiat dlfierent speeds in the two directions comprising two field windings one of which is connected across the line and the other across the mocurrent through the latter field winding and tor armature, means for reversing the current in the latter field winding and the armature of said motor, a dynamic braking circuit supplied with alternating current from the motor armature, and means for maintaining the dynamic braking circuit until the motor hasbeen brought substantially to rest before reversing the current in the said latter field winding and the moor armature. i 4. In a control system for electric motors, a reversible direct current motor, means for dynamically braking the same comprising a circuit supplied with alternating current from the motor armature, an impedance in said circuit, a pilot switch-for controlling the operationof said motor in both directions, means whereby the operation of said pilot switch causes the closure of the alteri nating current circuit to apply a dynamic brake to the motor and simultaneously causes the opening of the supply of current to'the motor, and means for causing the motor to operate at difierent speeds in the two directions comprising field windings one of which is connected across the line and the other across the motor armature.

5. In a system of motor control, a direct current motor, a supply circuit therefor, a dynamic braking circuit supplied with alternating current from the motor armature,

, and means responsive to the speed of the motor operative after the supplv circuit has been opened to maintain the dynamic braking circuit until the motor has been brought 100 substantially to rest and then close the supplyv circuit.- I

6. In a system of motor control, a reversible direct current motor having two permanently connected shunt fields, a sup ply circuit therefor, a dynamic braking cir-' cuit supplied with alternating current from the motor armature, and means responsive 'to the speed of themotor operative after the supply circuit has been opened to maintain the dynamic braking circuit until the motor has been brought substantially to .rest and then reverse the current to the motor armature and one of the field circuits, p

7. In a svstem of motor control, a direct A currentmotor, a supplv circuit therefor, a dynamic braking circuit supplied-with alternating current from the motor armature, a device for controllin saidcircuits having means tending to close the supply circuit and o en the braking circuit, and means for "restrainin the tendency of the first --mentioned means until the motor has been broughtsubstantially to rest.

8. In combination a direct current motor having an armature winding, said armature winding being provided with a commutator and slip ringsya supplv circuit leading to said commutator, a braking circuit leading I to said slip rings, means for controlling said circuits comprising an electromagnetic device having a winding tending to close the supply circuit and open the braking circuit and another winding restraining the tendency of the first winding until the motor has been brought substantially .to rest.

9. In combination, a direct current motor having an armature winding, said armature winding being provided with a commutator and slip rings, a supplv circuit leading to said commutator, a braking circuit leading to said slip rings, means for controlling said circuits comprising an'electromagnetic device haying a winding tending to close thesupply circuit and open the braking circuit and another winding responsive to the potential across said commutator for restraining the tendency of the first winding until the motor has been brought substantially to rest. a 4

10. In a system of motor control, a'reversibletdirect current motor, a supply circuit therefor, a dynamic braking circuit supplied with alternating current from the motor armature, a reversing controller for the motor, and an electromagnetically controlled switching device operated responsively to the movement of the reversing con- I .troller to open the surmly circuit and close the braking circuit, the said device having a winding responsive to the potential of the motor armature for maintaining the supply circuit open until the motorhas been brought substantially to rest.

11. In a system of motor control, a reversible direct current motor, a supply circuit therefor, a reversing controller therefor, a dynamic braking circuit for the motor supplied with alternating current from the motor armature, and an electromagnetically controlled switching device operated responsively to the movement of the reversing controller for opening the supply circuit and closing the braking circuit for both directions of rotation of the motor armature, the said device having' a winding energized from the motor armature for maintaining the supply circuit open until the motor has been brought substantially to rest.

In witness whereof, I have hereunto set "my hand this 18th day of November, 1913.

CARL P. TAYLOR.

Witnesses: r

Lnoiumn T. BLAISDELL, WniLrAnH. Wnrm, JR. 

